The present invention relates to a method and apparatus for knurling a pattern having two or more different configurations of grooves in a workpiece, and an article molded with the knurled workpiece. Such a molded article is useful for making an abrasive article in which a structured abrasive coating is provided on a substrate, among many other uses.
Two general methods of knurling are known. Knurling is typically performed by the first knurling process, referred to as roll knurling or form knurling. Form knurling is done by pressing a knurling wheel against a workpiece with sufficient force to plastically deform the outer surface of the workpiece. The second knurling process, referred to as cut knurling, is performed by orienting the knurling wheel relative to the workpiece such that the wheel cuts a pattern into the workpiece by removing metal chips. Cutting knurl holders and cutting knurl wheels are available from Dorian Tool International, Houston, Tex. Zeus brand cutting knurl tools are available from Eagle Rock Technologies Int""l Corp. of Bath, Pa.
In form knurling, the rotational axis of the knurl wheel is parallel to the rotational axis of the cylindrical workpiece. Therefore, the helix angle of the grooves formed on the roll is defined by the helix angle of the teeth on the knurl wheel. For cut knurling, the rotational axis of the cutting knurl wheel is tilted with respect to the rotational axis of the cylindrical workpiece (xe2x80x9cthe tilt anglexe2x80x9d) to define the helix angle and to produce the cutting action. Because the edge of the knurl wheel is being used as a cutting tool, it is necessary to provide a clearance angle. This is achieved by positioning the knurl wheel so that at the point of contact of the knurl wheel and workpiece surface, the toothed cylindrical surface of the knurl wheel and the workpiece surface form an angle of 3 to 10 degrees.
In both of the above types of knurling processes, the structure generated in the workpiece is a plurality of continuous grooves having a cross-section similar to the shape of the teeth on the knurl wheel. Both conventional knurling processes typically impart a diamond-based pattern which is the result of the intersection of two sets of continuous grooves, the two sets having opposite and equal helix angles (one having a left hand (xe2x80x9cLHxe2x80x9d) helix and one having a right hand (xe2x80x9cRHxe2x80x9d) helix) relative to a cylindrical workpiece. The intersection of the two sets of grooves creates a diamond pattern in the outer surface of the workpiece. The diamonds are aligned in the direction perpendicular to the longitudinal axis of the cylindrical workpiece, and are all substantially identical to one another. Conventional knurling processes have also been used to impart a square-based pattern, in which the squares are oriented to have their sides at 45xc2x0 to the longitudinal axis of the workpiece. As with the diamond-based pattern, the square-based pattern is also aligned in the direction perpendicular to the longitudinal axis of the cylindrical workpiece, and all of the square-based pyramids are identical. These processes are typically used to impart a non-slip pattern on a tool handle, machine control knob, or the like.
In common commercially available cut knurling holders, the knurl wheel tilt angle is fixed at xc2x130xc2x0 relative to the rotational axis of the cylindrical workpiece. Holders providing a xc2x145xc2x0 knurl wheel tilt angles are also available. Knurl wheels with teeth having helix angles relative to the rotational axis of the wheel of 0xc2x0, 15xc2x0 RH, 30xc2x0 RH, 15xc2x0 LH and 30xc2x0 LH are readily available. The sum of the tilt angle and the tooth helix angle defines the groove helix angle in the workpiece. The permutations of arithmetic sums of these wheel axis tilt angles and knurl teeth helix angles can produce groove helix angles on the cylindrical workpiece surface at 0xc2x0, 15xc2x0, 30xc2x0, 45xc2x0, 60xc2x0 and 75xc2x0 RH or LH to the workpiece rotational axis. If a groove helix angle on the workpiece surface other than these angles is desired, a special knurl wheel and/or knurl holder must be fabricated.
WIPO International Patent Application Publication Number WO 97/12727, published on Apr. 10, 1997, xe2x80x9cMethod and Apparatus for Knurling a Workpiece, Method of Molding an Article With Such Workpiece, and Such Molded Article,xe2x80x9d Hoopman et al., discloses a method and apparatus for knurling a workpiece in which the two sets of intersecting grooves each have a helix angle of unequal magnitude and opposite direction. The resulting knurl pattern is therefore not aligned in the cylindrical direction of the workpiece. Hoopman et al. also discloses a method of molding a molded article with the knurled workpiece to impart the inverse of the knurl pattern onto the molded article, and a method of forming a structured abrasive article with the molded article. The structured abrasive coating comprises abrasive particles and a binder in the form of a precise, three dimensional abrasive composites molded onto the substrate.
Other structured abrasives, and methods and apparatuses for making such structured abrasives, are described in U.S. Pat. No. 5,152,917, xe2x80x9cStructured Abrasive Article,xe2x80x9d (Pieper et al.), issued Oct. 6, 1992, the entire disclosure of which is incorporated herein by reference.
WIPO International Patent Application Publication Number WO 95/07797, xe2x80x9cAbrasive Article, Method of Manufacture of Same, Method of Using Same for Finishing, And a Production Tool,xe2x80x9d (Hoopman et al.), published Mar. 23, 1995, discloses a structured abrasive article in which the abrasive composites are not all identical. Hoopman et al. provides differing dimensioned shapes, among other things, in the array of abrasive composites. A copy of a desired pattern of variably dimensioned shapes of abrasive composites can be formed in the surface of a so-called metal master, e.g., aluminum, copper, bronze, or a plastic master such as acrylic plastic, either of which can be nickel-plated after grooving, as by diamond turning grooves to leave upraised portions corresponding to the desired predetermined shapes of the abrasive composites. Then, flexible plastic production tooling can be formed, in general, from the master by a method explained in U.S. Pat. No. 5,152,917 (Pieper et al.).
Other examples of structured abrasives and methods and apparatuses for their manufacture are disclosed in U.S. Pat. No. 5,435,816, xe2x80x9cMethod of Making an Abrasive Article,xe2x80x9d (Spurgeon et al.), issued Jul. 25, 1995, the entire disclosure of which is incorporated herein by reference. In one embodiment, Spurgeon et al. teaches a method of making an abrasive article comprising precisely spaced and oriented abrasive composites bonded to a backing sheet. Spurgeon et al. teaches that, in addition to other procedures, a thermoplastic production tool can be made according to the following procedure. A master tool is first provided. The master tool is preferably made from metal, e.g., nickel. The master tool can be fabricated by any conventional technique, such as engraving, hobbing, knurling, electroforming, diamond turning, laser machining, etc. The master tool should have the inverse of the pattern for the production tool on the surface thereof. The thermoplastic material can be embossed with the master tool to form the pattern. While Spurgeon et al. mentions briefly that the master tool can be made by knurling, no specific method of knurling a master tool is shown, taught, or suggested by Spurgeon et al.
Thus it is seen that there is a need for a knurling apparatus and method that allows the knurl wheel to be held at any desired angle relative to the rotational axis of a cylindrical workpiece. There is also a need to provide a knurling apparatus and method in which the knurling pattern in the workpiece comprises groove structures of at least two different configurations.
One aspect of the present invention provides a method of knurling a cylindrical surface of a workpiece, the workpiece having a longitudinal axis. The method comprises the steps of: a) imparting a first plurality of grooves to a workpiece, wherein the first plurality of grooves has a first helix angle with respect to the longitudinal axis of the workpiece; wherein the first plurality of grooves includes a first groove and a second groove, the second groove being of substantially different configuration from the first groove; and b) imparting a second plurality of grooves to the workpiece, wherein the second plurality of grooves has a second helix angle with respect to the longitudinal axis. The second plurality of grooves intersects the first plurality of grooves, thereby imparting a knurl pattern to the outer surface of the workpiece.
In one preferred embodiment of the above method, the second plurality of grooves includes a third groove and a fourth groove, the fourth groove being of substantially different configuration from the third groove. In one preferred version of this embodiment, the third and fourth grooves each comprise a first groove surface, a second groove surface, and a groove base. The first and second groove surfaces each extend from an outer surface of the workpiece to the groove base. The groove surfaces of the third groove are at a third included angle to one another, the surfaces of the fourth groove are at a fourth included angle to one another, and the fourth included angle is substantially different from the third included angle. In one preferred embodiment, the third and fourth included angles differ by at least 3 degrees. In another preferred embodiment, the third and fourth included angles differ by at least 10 degrees.
In another preferred embodiment of the above method, the first and second grooves each comprise a first groove surface, a second groove surface, and a groove base. The first and second groove surfaces each extend from an outer surface of the workpiece to the groove base. The groove surfaces of the first groove are at a first included angle to one another, and the surfaces of the second groove are at a second included angle to one another. The second included angle is substantially different from the first included angle. In one preferred version of this embodiment, the first and second included angles differ by at least 3 degrees. In another preferred version of this embodiment, the first and second included angles differ by at least 10 degrees. In another preferred version of this embodiment, the groove base is a line formed at the juncture of the first and second groove surfaces.
In yet another preferred embodiment of the above method, the intersection of the first plurality of grooves and second plurality of grooves forms a plurality of pyramids on the outer surface of the workpiece. Each of said pyramids includes first opposed side surfaces formed by the first grooves and second opposed side surfaces formed by the second grooves. The plurality of pyramids includes a first pyramid and a second pyramid, the second pyramid being of substantially different configuration from the first pyramid. In one preferred embodiment, the opposed first sides of the first pyramid form a first angle therebetween, the opposed first surfaces of the second pyramid form a second angle therebetween, and the second angle is at least 3 degrees different from the first angle. In another preferred embodiment, the second angle is at least 10 degrees different from the first angle. In another preferred embodiment, the pyramids are truncated pyramids.
In still another preferred embodiment of the above method, the pattern is continuous and uninterrupted around the circumference of the workpiece.
In still another preferred embodiment of the above method, the first and second groove helix angles are of substantially unequal magnitude.
Another aspect of the present invention provides a knurled workpiece made according to the above method.
Yet another aspect of the present invention provides a method of molding a molded article with the just-described knurled workpiece. This method comprises the steps of: a) applying a moldable material to the outer surface of the workpiece; b) while the moldable material is in contact with the workpiece, applying sufficient force to the moldable material to impart the inverse of the pattern on the outer surface of the workpiece to a first surface of the moldable material in contact with the workpiece; and c) removing the moldable material from the workpiece.
In yet another aspect, the present invention provides a molded article made in accordance with the just-described method.
The present invention also provides a knurled workpiece having a knurled, cylindrical outer surface. The knurled workpiece comprises: a cylindrical body having a longitudinal axis and an outer cylindrical surface, the outer surface having a knurl pattern thereon. The knurl pattern comprises a first plurality of grooves having a first helix angle with respect to the longitudinal axis of said workpiece. The first plurality of grooves includes a first groove and a second groove, the second groove being of a substantially different configuration from said first groove. The knurl pattern also comprises a second plurality of grooves. The second plurality of grooves has a second helix angle with respect to the longitudinal axis. The second plurality of grooves intersects the first plurality of grooves.
In one preferred embodiment of the above knurled workpiece, the second plurality of grooves includes a third groove and a fourth groove, the fourth groove being of a substantially different configuration from the third groove.
In another preferred embodiment of the above knurled workpiece, the first and second grooves each comprise a first groove surface, a second groove surface, and a groove base. The first and second groove surfaces each extend from the workpiece outer surface to the groove base. The groove surfaces of the first groove are at a first included angle to one another and the groove surfaces of the second groove are at a second included angle to one another, the second included angle being substantially different from the first included angle. In one preferred embodiment, the first and second included angles differ by at least 3 degrees. In another preferred embodiment, the first and second included angles differ by at least 10 degrees.
In another preferred embodiment of the above knurled workpiece, the third and fourth grooves each comprise a first groove surface, a second groove surface, and a groove base. The first and second groove surfaces each extend from the workpiece outer surface to the groove base. The groove surfaces of the third groove are at a third included angle to one another and the groove surfaces of the fourth groove are at a fourth included angle to one another, the fourth included angle being substantially different from the third included angle. In one preferred embodiment, the third and fourth included angles differ by at least 3 degrees. In another preferred embodiment, the third and fourth included angles differ by at least 10 degrees.
In another preferred embodiment of the above knurled workpiece, the groove base is a line formed at the juncture of the first and second groove surfaces.
In another preferred embodiment of the above knurled workpiece, the intersection of the first plurality of grooves and the second plurality of grooves forms a plurality of pyramids on the workpiece outer surface. Each of the pyramids includes first opposed side surfaces formed by the first grooves and second opposed side surfaces formed by the second grooves. The plurality of pyramids includes a first pyramid and a second pyramid, the second pyramid being of substantially different configuration from the first pyramid. In one version of this embodiment, the opposed first sides of the first pyramid form a first angle therebetween, and the opposed first surfaces of the second pyramid form a second angle therebetween, and the second angle is at least 3 degrees different from the first angle. In one embodiment, the second angle is at least 10 degrees different from the first angle.
In another preferred embodiment of the above knurled workpiece, the pyramids are truncated pyramids.
In another preferred embodiment of the above knurled workpiece, the knurl pattern is continuous and uninterrupted around the circumference of the workpiece.
In another aspect, the present invention provides a method of molding a molded article with the above knurled workpiece. The method comprises the steps of:
a) applying a moldable material to the outer surface of the knurled workpiece;
b) while the moldable material is in contact with the knurled workpiece, applying sufficient force to the moldable material to impart the inverse of the pattern on the outer surface of the knurled workpiece to a first surface of the moldable material in contact with the knurled workpiece; and c) removing the moldable material from the knurled workpiece.
In another aspect, the present invention provides a molded article made in accordance with the just-described method.
In yet another aspect, the present invention provides an apparatus for holding a cutting knurl wheel. The apparatus comprises a main support body; a shaft including a first end, a second end, and a longitudinal axis, wherein the shaft is rotatably mounted in the main body so as to rotate about the longitudinal axis; a knurl wheel mount on the second end of the shaft; a knurl wheel rotatably mounted on the knurl wheel mount so as to rotate about a knurl wheel axis, the knurl wheel including a plurality of teeth on an outer periphery thereof. The knurl wheel axis intersects the shaft longitudinal axis at an oblique angle. Rotation of the knurl wheel about the knurl wheel axis defines a distal point that is the location furthest in the direction from the first end of the shaft to the second end of the shaft through which the knurl teeth pass. The distal point is on the shaft longitudinal axis. The knurl wheel mount and knurl wheel are configured such that the distal point remains located on the shaft longitudinal axis during rotation of the shaft about the longitudinal axis. In one preferred embodiment, the shaft longitudinal axis and the knurl wheel axis intersect at an angle of from 80 to 87 degrees.
In still another aspect, the present invention provides a knurl wheel. The knurl wheel comprises: a body including first and second major opposed surfaces and an outer peripheral surface between the first and second major surfaces; and a plurality of teeth on the outer peripheral surface. The plurality of teeth include a first tooth and a second tooth, the second tooth being of substantially different configuration from the first tooth.
In one preferred embodiment of the above knurl wheel, the first tooth includes first and second sides extending from the outer peripheral surface, the first and second sides forming a first included angle therebetween. The second tooth includes third and fourth sides extending from the outer peripheral surface and defining a second included angle therebetween, the second angle being substantially different from the first angle. In one preferred embodiment, the second angle differs from the first angle by at least 3 degrees. In another preferred embodiment, the second angle differs from the first angle by at least 10 degrees.
In another preferred embodiment of the above knurl wheel, each of the plurality of teeth have a substantially different configuration.
In another preferred embodiment of the above knurl wheel, each of the teeth includes a first side and a second side extending from the outer peripheral surface. A respective first edge of one of the teeth and a respective second edge of an adjacent one of the teeth form an included angle therebetween, thereby forming a plurality of included angles between each adjacent pair of teeth. A first one of the included angles is substantially different from a second one of the included angles. In one preferred embodiment, the first included angle differs from the second included angle by at least 3 degrees. In another preferred embodiment, the first included angle differs from the second included angle by at least 10 degrees. In another preferred embodiment, each of the included angles is substantially different.